In U.S. Pat. No. 4,085,644 there is described a polyphonic tone synthesizer which generates a group of musical notes in response to actuation of keys on a keyboard by computing a master data list which defines the waveshape of each individual tone. The instrument may have a number of keyboards of divisions. A group of stops controls the waveform associated with the keys of each individual keyboard. In Pat. No. 4,022,098 there is described a keyboard switch detect and assignor circuit by means of which data identifying the note octave and keyboard of each key that is operated is stored in an assignment memory. This data is continuously updated as keys are released and new keys are actuated. The data in the assignment memory is used to control a group of tone generators for generating the corresponding audible tones. The present invention is directed to a modification to the keyboard switch detect and assignor circuit of U.S. Pat. No. 4,022,098, which is hereby incorporated by reference, to insert automatically note data into the assignment memory in response to operation of a selected key on the keyboard of harmonically related notes. The polyphonic tone synthesizer, in response to the information stored in the assignment memory, then generates the harmonically related tones.
Automatic harmony in electronic organs has heretofore been proposed. Such arrangements have derived information from the accompaniment played on a separate keyboard to select the harmonically related notes. Such known arrangements have the disadvantage that the harmonious note in the melody line could only be obtained if an accompaniment chord is played. However, if the accompaniment is played in a rhythm, then the harmonic note in the melody line is forced to follow the same rhythm. In addition, such known automatic harmony systems have been limited to generating a harmony note that has the same tonal quality as the melody note.
The present invention provides an improved automatic harmony generator in which harmonic tones can be generated in the melody line even when an accompaniment note is not played and in which the harmonic note may have a different tonal characteristic than the melody note.